bio 224 exam 4

urinary system

About how much can you have missing from this organ system while still having it function?

You can have up to 75-80% of the organs (the kidneys) missing & it’d still function!

functions of the urinary system (4 total) (it’s all about fluid regulation!)

• regulating blood…

  • volume

  • contents

  • concentration

  • blood pressure

• Make EPO (hormone)

• Make renin (enzyme)

• Excretion of waste (in urine)

Kidney location

• It’s retroperitoneal (behind the peritoneum)

• Anchored to the dorsal body wall T₁₂-L₃ by some adipose

Ptosis

• When a kidney slumps. This can kink up the hoses & lead to death.

• Often caused by severe loss of conn. tissue

Kidney anatomy (9 structures/parts to list) (list the length & weight as well!)

• 5” tall & 130g

• Renal Cortex- the outer part

• Renal Medulla- the inner part.

  • Renal pyramid- the triangle shaped part of the medulla.

    • Papilla- the tip of the pyramid. This is where urine comes out

  • Renal column- the structure between the renal pyramids

• Minor calyx- the channel coming from just one pyramid

• Major calyx- where 2 or more minor calyces meet

• Renal pelvis- where all the major calyces meet

• Hilum- dent in the organ that tubes go in & out of

What percentage of your body’s blood is in your kidneys?

About 25%

Blood flow in the kidneys (13 parts)

• Renal artery

• Segmental artery

• Interlobar artery

• Arcuate artery

• Cortical radiate artery

• Afferent arteriole

• Glomerulus (a capillary bed where no gas exchange occurs since an arteriole goes out)

• Efferent arteriole

• Peritubular capillaries (perform gas exchange)

• Cortical radiate vein

• Arcuate vein

• Interlobar vein

• Renal vein

Nephron

• The functional unit of the kidney

• It’s the tubule & all the blood vessels associated with it from the arcuate artery to the arcuate vein)

• We have about 2.6 million nephrons in our body

Anatomy of the nephron tubule (snake shaped part) (5 parts)

• Bowman’s capsule- the “snake head” of the nephron tubule

• Proximal convoluted tubule- the “neck” of the “snake”, connected to the head with many turns

• Loop of Henle- the “large U-turn”

• Distal convoluted tubule- the twisty end of the “snake” with the end connecting to the collecting duct

• Collecting duct- the duct at the end of the “snake”

Blood vessels of the nephron (8 parts)

• Arcuate artery

• Cortical radiate artery

• Afferent arteriole (larger in diameter than the efferent arteriole)

• Glomerulus (the odd capillary in the “mouth” of the snake)

• Efferent arteriole

• Peritubular capillary

• Cortical radiate vein

• Arcuate vein

3 processes in a nephron & where they occur. What do these processes form?

• Filtration= F (occurs in glomerulus & Bowman’s capsule) (the renal corpuscle)

• Reabsorption= R (Proximal convoluted tubule, Loop of Henle, & Distal Convoluted Tubule/Collecting Duct) (or PCT, LH, & DCT/CD)

• Secretion= S (Proximal convoluted tubule & Distal Convoluted Tubule/Collecting Duct) (or PCT & DCT/CD)

these processes form URINE

What process(es) occur(s) in Bowman’s Capsule & Glomerulus (BC & G)? (these two are part of the renal corpuscle)

filtration. F

What process(es) occur(s) in Proximal Convoluted Tubule (PCT)?

mostly reabsorption & some secretion. Rs

What process(es) occur(s) in Loop of Henle (LH)?

reabsorption. R

What process(es) occur(s) in Distal Convoluted Tubule/Collecting Duct (DCT/CD)?

• Reabsorption and/or secretion, depending on our needs. R and/or S

• This is where variability occurs

• note: DCT & CD are anatomically different structures, but physiologically the same unit

filtrate

fluid in the nephron tubule. Formed after filtration

filtration, reabsorption & secretion

• Filtration- the glomerulus leaks since it’s a capillary (all capillaries leak all the time). Plasma leaks out of blood into Bowman’s Capsule, which has holes in it. These holes in BC allow for filtration

• Reabsorption-reabsorb things from filtrate (fluid in nephron tubule) into tubule (in peritubular capillary)

  • Absorb something that was previously lost, thus absorbing it a second time

• Secretion- secrete from blood into filtrate

What enters & exits from the nephron tubule?

• Blood plasma enters thru the renal corpuscle (BC & G)

• Urine exits thru the collecting duct (CD)

Types of nephrons (2 types. List general location & percentages)

• Cortical nephrons- makes up 80-85% of our nephrons. These are mostly in the cortex

• Juxtamedullary nephrons- makes up about 15% of our nephrons. These dip way down into the medulla

Filtration (Define filtration & 4 terms/structures to know associated with it)

• Filtration- blood plasma moving from bloodstream into nephron through holes

• Only occurs at glomerulus & Bowman’s capsule

  • BC wraps around Glomerulus, like a catcher’s mitt wrapped around a ball

• Podocytes- inner layer of BC. covers up glomerulus & lays against the capillary. This is where filtration occurs

  • Filtration slits- gaps in the BC, between podocytes

• Fenestrations- little holes in blood vessel.

• Filtration membrane- found where the fenestrations & filtration slits are

Filtration pressures (list the forces that favor & oppose filtration & the net filtration pressure)

blood side 50mmHg→ ←40mmHg filtrate side

• Force favoring filtration (making filtrate): BP→ 50mmHg (pushing from blood to filtrate)

  • BP in glomerulus: 50 mmHg pushing out plasma out of the glomerulus

• Forces opposing filtration (don’t want to make filtrate): 40mmHg← osmotic pressure of G & fluid pressure of BC (pushing from filtrate to blood)

  • Fluid pressure of BC: 30mmHg

  • Osmotic pressure of G: 10 mmHg

• Net filtration pressure (NFP): 10mmHg → (drives fluid out of glomerulus).

  • Favoring filtration wins, but not by much

Glomerular filtration rate (How much do we filter per minute & per day?)

• 125ml/min

• 180L/day

This is how much filtrate we make (not urine. We make less urine than filtrate)

Caffeine’s effect on urine volume

Consuming caffeine increases BP, so the 50mmHg pushing to make filtrate (force favoring filtration) increases. This causes more filtration & more urination

What are the “big stars” of reabsorption & secretion?

Na⁺ & H₂O

• Water follows Na⁺, when it can when it’s allowed (when the cell membrane permeability lets it)

How is sodium reabsorbed? Water? (Includes structure for water to get through the CM)

• Sodium

  • is reabsorbed by pumping it (active transport)

  • It gets pumped in, then pumped out into blood. The more the pumps work, the more sodium we get in blood.

    • This blood in the peritubular capillary becomes very concentrated, so it’ll pull on water thru osmosis

• Water

  • follows sodium by diffusion/osmosis when cell membrane permeability allows

  • Aquaporins- Proteins that are tunnels for water in the cell membrane.

    • Water can only follow sodium by entering aquaporins since the CM is made of lipids

How does glucose get reabsorbed?

• Glucose gets co-transported with sodium. In other words, it hitches a ride with sodium as it gets pumped

Reabsorption percentages for the PCT (4 items to list)

• 65% of H₂O

• 65% of Na⁺

• 100% of glucose, amino acids, & other organic solutes (thru cotransport with Na⁺)

  • If glucose/proteins/etc. are found in urine, this can indicate an issue with the kidney (the PCT specifically) since it should reabsorb all of it

• 90% of HCO₃^- (bicarbonates)

Can you get water out of the Loop of Henle? If so, what’s the catch?

• Yes, you can get H₂O out of the Loop of Henle, but it’ll be more difficult

The Countercurrent system in the Loop of Henle (aka the “Double Whammy!”)

• Descending Limb

  • Has PCT leading into it & filtrate moves down

  • Thinner

  • IS permeable to water (has aquaporins)

  • Reabsorbs 25% of H₂O

• Ascending limb

  • Leads out into DCT & filtrate moves up

  • Thicker

  • NOT permeable to water (has no aquaporins)

  • Pumps out Na⁺ & Cl^- (chlorine)

  • Reabsorbs 25% of Na⁺ & Cl^-

• Sodium gets pumped out into the trough (area between each limb) & makes it more concentrated, so the water from the descending limb gets drawn out thru osmosis.

• The more sodium coming out of the ascending limb, the more water comes from the descending limb. This allows it to continuously escalate.

  • Gets more Na⁺ & Cl^- out of filtrate

• This is a positive feedback mechanism that doesn’t stop bc filtrate constantly goes in & out

Countercurrent exchange & countercurrent multiplication

• Countercurrent exchange- the 2 sides are trading substances (water for Na⁺ & Cl^- )

• Countercurrent multiplication- concentration is changing (increasing in descending limb, decreasing in ascending limb)

How much Na⁺ & H₂O is left in the nephron by the time filtrate reaches the DCT? (after the loop of Henle)

10% each

Reabsorption at the DCT & CD

• 10% of Na⁺ & H₂O is still in the filtrate, which can either get reabsorbed by the capillary or can do nothing

• In the DCT, you can either:

  • save it (reabsorption)

  • Let it pass (leave it & urinate it out)

• This is where we adjust the urine depending on our needs

  • The “fine tuners” are our hormones

Diuresis

making urine

Diuretics

Increases urine production

ADH (antidiuretic hormone)

• List what it’s made by, target cells, command, & effects (2 main effects)

• Made by: hypothalamus (released by posterior pituitary gland)

• Target cells: DCT/CD

• Command: Inc. H₂O reabsorption

  • make more aquaporin-2 (temporary doorways) (aquaporin-1 is permanent)

• Effects:

  • Dec. urine volume

  • Inc. urine concentration (keep water in blood, which will inc. blood vol.)

  • “SAVE THE H₂O”

Aldosterone

• List what it’s made by, target cells, command, & effects (1 effect)

• Made by: Adrenal cortex

• Target cells: DCT/CD

• Command: Inc. Na⁺ reabsorption

  • more Na⁺ pumping

• Effects:

  • Dec. urine concentration

    • H₂O follows when ADH is present

    • by itself, aldosterone doesn’t change the volume, just the concentration

  • “SAVE THE Na⁺”

ANH/ANP (Atrial Natriuretic Hormone)

• List what it’s made by, target cells, commands (2 commands), & effects (3 effects)

• Made by: Right atrium when overstretched (meaning too much blood in the atrium)

  • think of it like a squid releasing ink in a panic. The right atrium doesn’t want to break, so it releases ANH in response to overstretching

• Target cells: Posterior Pituitary Gland (where ADH is released) & DCT/CD

• Command: Dec. ADH release & Dec. Na⁺ reabsorption

  • It’s saying “LOSE THEM BOTH!!” (doesn’t want water & sodium to get reabsorbed back into blood)

• Effects:

  • Na⁺ & H₂O stay in urine

  • Large volume of normal to dilute urine

    • Overkill to get rid of sodium, but it’s done just to be safe

  • Dec. blood volume

    • helps prevent the atrium from overstretching

  • “DUMP ‘EM BOTH”

Chronic diabetes insipidus

• Hyposecretion of ADH. Water can’t be saved & stays in urine

  • Results in high urine volume (peeing all the time).

  • Water doesn’t get shifted back to blood at the DCT/CD

Alcohol’s effect on urine volume

Alcohol reduces the ability to produce ADH by inhibiting the hypothalamus, thus increasing urine volume

BNH or B-Type ANH

• This is a version of ANH that’s made by the ventricles

  • This is normally less than 20% of total ANH

  • If/when it becomes more than 20%, this is a sign of heart failure

Renin-angiotensin-aldosterone-ADH-system

• list where this fluid regulatory mechanism occurs (including what it’s composed of), what causes the release of renin, the enzymes involved, & the 5 effects

• Juxtaglomerular apparatus: combo of 2 cells in the nephron:

  • Juxtaglomerular cells

    • Smooth musc. cells that surround afferent arteriole

    • Filled with the enzyme renin

    • These monitor blood pressure in afferent arteriole

  • Macula densa cells

    • Cells in the wall of DCT

    • monitor filtrate concentration

• Release of renin: caused by Low BP (in afferent arteriole) or low filtrate concentration (in DCT)

• angiotensinogen (inactive form in blood made by liver —renin→ angiotensin I (occurs in blood)

• angiotensin I —ACE (angiotensin converting enzyme)→ angiotensin II (occurs in lungs)

  • Angiotensin II is a powerful vasoconstrictor

• Effects:

  • Inc. ADH release

  • Inc. Aldosterone release (save them both!)

  • Dec. Urine volume

  • Inc. Blood volume

  • Vessels constricted (inc. BP)

Secretions

• This is what we add to filtrate before we urinate

• Substances are secreted by countertransport with sodium (pumped in different directions)

Secretions at PCT & DCT/CD

PCT

• H⁺

• Nitrogenous wastes

• Some drugs

DCT/CD

• H⁺

Nitrogenous wastes found in urine & how they’re made (4)

• urea- from deamination (remove aminos) of prots. by liver (protein metabolism)

• NH₄⁺ (ammonium) - from the same as above

• uric acid- from decomposition of nucleic acids (DNA/RNA)

• creatinine- from CP (creatine phosphate) breakdown

  • can be dangerous when there’s too much due to muscle injuries (large rips of muscle tissue). Can result in kidney failure

abnormal urine contents & possible reasons for abnormalities (just 1 abnormality to list that can be found in urine) (2 reasons for abnormality)

• Glucose- the glucose should be fully absorbed in the PCT, along with proteins & amino acids.

  • Either caused by…

    • too much glucose in blood that it can’t be reabsorbed fast enough

    • broken PCT

Urinary bladder

list the location, how much it can hold, what epithelium lines the urinary bladder, the 4 structures, & the openings

• Located behind pubic symphysis

• Volume can expand up to 1L thanks to rugae

• Lined with transitional epithelium

• Has 3 openings

  • 2 ureteral openings & 1 urethral opening to form the trigone

• Urethra- urine tube at the bottom of urinary bladder

• Detrusor muscle- specialized smooth musc. that lines the bladder

  • 2 layers of longitudinal smooth musc fibers with 1 layer of circular in between

• Internal urethral sphincter- smooth musc.

• External urethral sphincter- skeletal musc. (we can control this)

Male vs. Female (in regards to the urethra & sphincters). Who is more prone to UTIs & why?

• Sphincters are easy to identify in males due to the prostate gland. Female have both sphincters, but it’s more difficult to identify

• Urethra in male is longer (20cm) while it’s shorter in females (3-5cm)

  • Causes women to be more prone to UTI (urinary tract infection)

    • This is bc there’s less of an opportunity to catch bacteria throughout the urethra

Micturition

list the definition, what triggers it, & what will contract & relax in response to the trigger.

• Micturition- voiding your bladder (peeing)

• Triggered when 200-300ml of urine shows up in bladder

  • Pushes against walls (distention)

• We have a short loop (causes reflex) & long loop (up to brain) (similar to defecation)

• Detrusor musc. contracts while internal & external urethral sphincters relax

  • Detrusor contracts to let urine out

  • Sphincters relax to open

• We learn to contract the external urethral sphincter to control urination

  • Events like childbirth, injuries or aging can cause us to lose the ability to control urination

hemodialysis

• temporarily removes a person’s blood & passes it thru a filter that removes metabolic wastes & extra fluid. This normalizes electrolyte & acid-base balance

• Must be performed 3 times per week at a dialysis clinic

peritoneal dialysis

• dialysis fluid is placed into the peritoneal cavity, allowed to circulate for several hours, then drained

• Can be performed nightly at home, so this is the preferred treatment for long-term dialysis

renal calculi (kidney stones)

• Crystalline structures composed most commonly of calcium oxalate salts. Formed due to high concentrations of ions in filtrate

  • These can adhere to the tubules

  • causes severe pain, blood in urine, sweating, nausea, & vomiting

glomerulonephritis

damage to & destruction of glomeruli, causing inflammation of glomerular capillaries & filtration membrane. Can lead to renal failure

incontinence

loss of voluntary control over the bladder. Can be caused by childbirth, injuries, or age

What percentage of a person is water for a female & a male? What causes these different percentages?

• Women: 50% water

  • Caused by more estrogen, meaning more subcutaneous adipose (our least hydrated tissue)

• Men: 60% water

  • Caused by more testosterone, meaning more skeletal musc (our most hydrated tissue)

Where is water located in the human body? (includes the definition for fluid compartment)

Fluid compartment- where the fluid is. Extracellular fluid is the largest fluid compartment.

Either one of the two fluid compartments…

• Extracellular fluid- outside cells. 40%

  • There are multiple kinds (ex. lymph, interstitial fluid, blood plasma, etc). These just get lumped together. Constantly moved around & similar.

• Intracellular fluid- inside cells. 60%

How we get water in & water out (~3 methods each)

• Gain water

  • Drinking

  • Eating

  • Making it (ex. from electron transport system)

• Lose water

  • Urinating (peeing)

  • Defecating (pooping)

  • Evaporation (ex. thru skin by sweating or thru lungs by exhaling water vapor)

• We want these to be equal for homeostasis. If not, we need to use fluid regulatory mechanisms

Blood plasma vs. interstitial fluid vs. intracellular fluid

• Blood plasma & interstitial fluid are both extracellular fluids (outside the cell)

  • However, plasma has a higher protein count

  • Extracellular fluid has more Na⁺

• Intracellular fluid is found inside the cell.

  • Has more K⁺ than extracellular fluid

  • Different from extracellular fluid due to the cell membrane.

Ion

a particle with a charge

cation vs. anion

• Cation- an ion with a positive charge

• Anion- an ion with a negative charge

Extracellular fluid (ECF) & Intracellular fluid (ICF)

• what do they have in them (3 each) & what causes them to be different?

• We expect the extracellular & intracellular fluid to be different due to the cell membrane!! That’s the cell membrane’s purpose (otherwise, we wouldn’t need one)

  • Ex. We have the sodium potassium pump to pump 3 sodium into ECF & 2 potassium into ICF

• ECF has more sodium, chlorine, & bicarbonates

• ICF has more potassium, proteins, & phosphates

electrolyte vs. nonelectrolyte

• electrolyte- A substance that will dissociate (come apart) when dissolved to form charged particles (ions)

  • Water containing ions will carry an electrical current

  • Mostly inorganic molecules (don’t contain carbon) (often called salts)

  • Acids & bases are electrolytes

• nonelectrolyte- A substance that will not come apart when dissolved, thus not breaking into ions

  • Tend to be organic molecules (ex. glucose)

  • Won’t carry a current

What are the most important ions related to acids & bases? Determine if something becomes more acidic or basic when more of each of these ions are present.

• The important ions are H⁺ & OH^-

• The more H⁺ = more acidic

• The more OH^- (or fewer H⁺) = more basic

pH scale

• Measures the strength of an acid or base based on how much H⁺ there is

• The scale is opposite. Lower pH = more H⁺, & vice versa

  • The further you are from pH 7 (neutral), the stronger & more dangerous the acid/base is

    • Ex. pH of 2 is very acidic & dangerous while a pH of 13 is very basic & dangerous

• Based in powers of 10

Acids vs. Bases(alkaline)

• What do they do with H⁺? What would the pH of each be? What substances tend to fall under each category?

• Acid- electrolytes that dissolve & give off H⁺. “H⁺ donors”

  • Almost always start with a hydrogen

  • pH is less than 7

• Base (alkaline)- electrolytes that bind up H⁺. “H⁺ acceptors”

  • Often hydroxides

    • Takes the H⁺ out of the solution, combine with OH^- to form water

  • pH is greater than 7

Why is it important to not have large shifts in pH in our bodies?

If we have large shifts in pH in our bodies, then enzymes won’t work & metabolism ends, which can lead to death

Human acidity vs. Human alkalinity (basicness).

• List the definitions & sources for each (sources for H⁺ & OH^-)

• Human acidity- pH goes down (becomes more acidic). Comes from metabolism

  • carbonic acid, lactic acid, sulfuric acid, phosphoric acid, fatty acids & ketones are made from metabolism

• Human alkalinity- pH goes up (becomes more basic).

  • Comes from eating K⁺, Mg⁺⁺, Ca⁺⁺, & Na⁺

What’s the normal pH range of human blood?

7.35-7.45

Buffers (list the 2 types)

Chemicals or actions that resist changes in pH

• Chemical buffers are limited since they can essentially get overwhelmed holding onto H⁺. These will eventually run out

• If it’s an action, it’s a physiological buffer, which is better since we can’t run out of these

Physiological buffer (list the 2 locations & functions for the human body’s buffer systems)

• An action buffer, which can’t run out.

• We have 2 types of physiological buffers:

  • Urinary system- can pee out H⁺ so they don’t build up in blood

    • Urine has a large pH range (pH of 4-8) to help make sure the blood pH doesn’t change

  • Respiratory system- can remove H⁺ by breathing out CO₂. Holding in your breath can make blood more acidic

    • Remember, respiratory rate affects blood CO₂ levels

acidosis vs. alkalosis

• acidosis= too acidic (pH too low)

  • blood pH is less than 7.35

• alkalosis= too basic (pH too high)

  • blood pH is greater than 7.45

Respiratory acidosis/alkalosis vs. Metabolic acidosis/alkalosis

• Respiratory- caused by respiratory system

  • The only cause of respiratory acidosis is hypoventilation.

    • pH too low, low resp. rate & high blood CO₂

  • Respiratory alkalosis is caused by hyperventilation

    • pH too high, high resp. rate & low blood CO₂

  • Can determine if it’s respiratory based on the respiratory rate.

• Metabolic- caused by anything that’s not the respiratory system

  • can have a variety of different causes, it’s just not caused by the res. sys

How fluid volume is controlled by each of the following:

• renin, aldosterone, ADH, ANH, & hypothalamus (hint! only one of these will decrease fluid volume)

• renin- inc. fluid volume since it wants to save sodium & water to inc. BP

• aldosterone- inc. fluid volume since it wants to save sodium, & water wants to follow sodium when it can & when it’s allowed.

• ADH- inc. fluid volume since it wants to keep H₂O in blood

• ANH- dec. fluid volume since it’s triggered by a high blood volume

• hypothalamus- inc. fluid volume by releasing ADH

hypernatremia vs. hyponatremia (include what it’s commonly caused by for each)

• hypernatremia- abnormal increase in plasma sodium ion concentration. Commonly caused by dehydration

• hyponatremia- abnormal decrease in the plasma sodium ion concentration. Commonly caused by overhydration

hyperkalemia vs. hypokalemia

• hyperkalemia- abnormally high potassium ion concentration, above 4.5 mEq/l

• hypokalemia- abnormally low potassium ion concentration, below 3.9 mEq/l

hypercalcemia vs. hypocalcemia

• hypercalcemia- abnormally high calcium ion concentration, above 10.5 mg/dl

• hypocalcemia- abnormally low calcium ion concentration, below 8.7 mg/dl

edema

swelling caused by excess water/fluid in interstitial fluid

Source & action of parathyroid hormone & calcitonin

• Parathyroid hormone (PTH)- source is the parathyroid gland

  • Increases blood calcium level by triggering calcium ion reabsorption in kidneys & osteoclast activity

• Calcitonin- source is the thyroid gland

  • Decreases blood calcium level by stimulating osteoblasts